[GitHub/mt8127/android_kernel_alcatel_ttab.git] / fs / notify / inode_mark.c

/*
 *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2, or (at your option)
 *  any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; see the file COPYING.  If not, write to
 *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/*
 * fsnotify inode mark locking/lifetime/and refcnting
 *
 * REFCNT:
 * The mark->refcnt tells how many "things" in the kernel currently are
 * referencing this object.  The object typically will live inside the kernel
 * with a refcnt of 2, one for each list it is on (i_list, g_list).  Any task
 * which can find this object holding the appropriete locks, can take a reference
 * and the object itself is guarenteed to survive until the reference is dropped.
 *
 * LOCKING:
 * There are 3 spinlocks involved with fsnotify inode marks and they MUST
 * be taken in order as follows:
 *
 * entry->lock
 * group->mark_lock
 * inode->i_lock
 *
 * entry->lock protects 2 things, entry->group and entry->inode.  You must hold
 * that lock to dereference either of these things (they could be NULL even with
 * the lock)
 *
 * group->mark_lock protects the mark_entries list anchored inside a given group
 * and each entry is hooked via the g_list.  It also sorta protects the
 * free_g_list, which when used is anchored by a private list on the stack of the
 * task which held the group->mark_lock.
 *
 * inode->i_lock protects the i_fsnotify_mark_entries list anchored inside a
 * given inode and each entry is hooked via the i_list. (and sorta the
 * free_i_list)
 *
 *
 * LIFETIME:
 * Inode marks survive between when they are added to an inode and when their
 * refcnt==0.
 *
 * The inode mark can be cleared for a number of different reasons including:
 * - The inode is unlinked for the last time.  (fsnotify_inode_remove)
 * - The inode is being evicted from cache. (fsnotify_inode_delete)
 * - The fs the inode is on is unmounted.  (fsnotify_inode_delete/fsnotify_unmount_inodes)
 * - Something explicitly requests that it be removed.  (fsnotify_destroy_mark_by_entry)
 * - The fsnotify_group associated with the mark is going away and all such marks
 *   need to be cleaned up. (fsnotify_clear_marks_by_group)
 *
 * Worst case we are given an inode and need to clean up all the marks on that
 * inode.  We take i_lock and walk the i_fsnotify_mark_entries safely.  For each
 * mark on the list we take a reference (so the mark can't disappear under us).
 * We remove that mark form the inode's list of marks and we add this mark to a
 * private list anchored on the stack using i_free_list;  At this point we no
 * longer fear anything finding the mark using the inode's list of marks.
 *
 * We can safely and locklessly run the private list on the stack of everything
 * we just unattached from the original inode.  For each mark on the private list
 * we grab the mark-> and can thus dereference mark->group and mark->inode.  If
 * we see the group and inode are not NULL we take those locks.  Now holding all
 * 3 locks we can completely remove the mark from other tasks finding it in the
 * future.  Remember, 10 things might already be referencing this mark, but they
 * better be holding a ref.  We drop our reference we took before we unhooked it
 * from the inode.  When the ref hits 0 we can free the mark.
 *
 * Very similarly for freeing by group, except we use free_g_list.
 *
 * This has the very interesting property of being able to run concurrently with
 * any (or all) other directions.
 */

#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <linux/writeback.h> /* for inode_lock */

#include <asm/atomic.h>

#include <linux/fsnotify_backend.h>
#include "fsnotify.h"

void fsnotify_get_mark(struct fsnotify_mark_entry *entry)
{
	atomic_inc(&entry->refcnt);
}

void fsnotify_put_mark(struct fsnotify_mark_entry *entry)
{
	if (atomic_dec_and_test(&entry->refcnt))
		entry->free_mark(entry);
}

/*
 * Recalculate the mask of events relevant to a given inode locked.
 */
static void fsnotify_recalc_inode_mask_locked(struct inode *inode)
{
	struct fsnotify_mark_entry *entry;
	struct hlist_node *pos;
	__u32 new_mask = 0;

	assert_spin_locked(&inode->i_lock);

	hlist_for_each_entry(entry, pos, &inode->i_fsnotify_mark_entries, i_list)
		new_mask |= entry->mask;
	inode->i_fsnotify_mask = new_mask;
}

/*
 * Recalculate the inode->i_fsnotify_mask, or the mask of all FS_* event types
 * any notifier is interested in hearing for this inode.
 */
void fsnotify_recalc_inode_mask(struct inode *inode)
{
	spin_lock(&inode->i_lock);
	fsnotify_recalc_inode_mask_locked(inode);
	spin_unlock(&inode->i_lock);

	__fsnotify_update_child_dentry_flags(inode);
}

/*
 * Any time a mark is getting freed we end up here.
 * The caller had better be holding a reference to this mark so we don't actually
 * do the final put under the entry->lock
 */
void fsnotify_destroy_mark_by_entry(struct fsnotify_mark_entry *entry)
{
	struct fsnotify_group *group;
	struct inode *inode;

	spin_lock(&entry->lock);

	group = entry->group;
	inode = entry->inode;

	BUG_ON(group && !inode);
	BUG_ON(!group && inode);

	/* if !group something else already marked this to die */
	if (!group) {
		spin_unlock(&entry->lock);
		return;
	}

	/* 1 from caller and 1 for being on i_list/g_list */
	BUG_ON(atomic_read(&entry->refcnt) < 2);

	spin_lock(&group->mark_lock);
	spin_lock(&inode->i_lock);

	hlist_del_init(&entry->i_list);
	entry->inode = NULL;

	list_del_init(&entry->g_list);
	entry->group = NULL;

	fsnotify_put_mark(entry); /* for i_list and g_list */

	/*
	 * this mark is now off the inode->i_fsnotify_mark_entries list and we
	 * hold the inode->i_lock, so this is the perfect time to update the
	 * inode->i_fsnotify_mask
	 */
	fsnotify_recalc_inode_mask_locked(inode);

	spin_unlock(&inode->i_lock);
	spin_unlock(&group->mark_lock);
	spin_unlock(&entry->lock);

	/*
	 * Some groups like to know that marks are being freed.  This is a
	 * callback to the group function to let it know that this entry
	 * is being freed.
	 */
	if (group->ops->freeing_mark)
		group->ops->freeing_mark(entry, group);

	/*
	 * __fsnotify_update_child_dentry_flags(inode);
	 *
	 * I really want to call that, but we can't, we have no idea if the inode
	 * still exists the second we drop the entry->lock.
	 *
	 * The next time an event arrive to this inode from one of it's children
	 * __fsnotify_parent will see that the inode doesn't care about it's
	 * children and will update all of these flags then.  So really this
	 * is just a lazy update (and could be a perf win...)
	 */


	iput(inode);

	/*
	 * it's possible that this group tried to destroy itself, but this
	 * this mark was simultaneously being freed by inode.  If that's the
	 * case, we finish freeing the group here.
	 */
	if (unlikely(atomic_dec_and_test(&group->num_marks)))
		fsnotify_final_destroy_group(group);
}

/*
 * Given a group, destroy all of the marks associated with that group.
 */
void fsnotify_clear_marks_by_group(struct fsnotify_group *group)
{
	struct fsnotify_mark_entry *lentry, *entry;
	LIST_HEAD(free_list);

	spin_lock(&group->mark_lock);
	list_for_each_entry_safe(entry, lentry, &group->mark_entries, g_list) {
		list_add(&entry->free_g_list, &free_list);
		list_del_init(&entry->g_list);
		fsnotify_get_mark(entry);
	}
	spin_unlock(&group->mark_lock);

	list_for_each_entry_safe(entry, lentry, &free_list, free_g_list) {
		fsnotify_destroy_mark_by_entry(entry);
		fsnotify_put_mark(entry);
	}
}

/*
 * Given an inode, destroy all of the marks associated with that inode.
 */
void fsnotify_clear_marks_by_inode(struct inode *inode)
{
	struct fsnotify_mark_entry *entry, *lentry;
	struct hlist_node *pos, *n;
	LIST_HEAD(free_list);

	spin_lock(&inode->i_lock);
	hlist_for_each_entry_safe(entry, pos, n, &inode->i_fsnotify_mark_entries, i_list) {
		list_add(&entry->free_i_list, &free_list);
		hlist_del_init(&entry->i_list);
		fsnotify_get_mark(entry);
	}
	spin_unlock(&inode->i_lock);

	list_for_each_entry_safe(entry, lentry, &free_list, free_i_list) {
		fsnotify_destroy_mark_by_entry(entry);
		fsnotify_put_mark(entry);
	}
}

/*
 * given a group and inode, find the mark associated with that combination.
 * if found take a reference to that mark and return it, else return NULL
 */
struct fsnotify_mark_entry *fsnotify_find_mark_entry(struct fsnotify_group *group,
						     struct inode *inode)
{
	struct fsnotify_mark_entry *entry;
	struct hlist_node *pos;

	assert_spin_locked(&inode->i_lock);

	hlist_for_each_entry(entry, pos, &inode->i_fsnotify_mark_entries, i_list) {
		if (entry->group == group) {
			fsnotify_get_mark(entry);
			return entry;
		}
	}
	return NULL;
}

/*
 * Nothing fancy, just initialize lists and locks and counters.
 */
void fsnotify_init_mark(struct fsnotify_mark_entry *entry,
			void (*free_mark)(struct fsnotify_mark_entry *entry))

{
	spin_lock_init(&entry->lock);
	atomic_set(&entry->refcnt, 1);
	INIT_HLIST_NODE(&entry->i_list);
	entry->group = NULL;
	entry->mask = 0;
	entry->inode = NULL;
	entry->free_mark = free_mark;
}

/*
 * Attach an initialized mark entry to a given group and inode.
 * These marks may be used for the fsnotify backend to determine which
 * event types should be delivered to which group and for which inodes.
 */
int fsnotify_add_mark(struct fsnotify_mark_entry *entry,
		      struct fsnotify_group *group, struct inode *inode)
{
	struct fsnotify_mark_entry *lentry;
	int ret = 0;

	inode = igrab(inode);
	if (unlikely(!inode))
		return -EINVAL;

	/*
	 * LOCKING ORDER!!!!
	 * entry->lock
	 * group->mark_lock
	 * inode->i_lock
	 */
	spin_lock(&entry->lock);
	spin_lock(&group->mark_lock);
	spin_lock(&inode->i_lock);

	lentry = fsnotify_find_mark_entry(group, inode);
	if (!lentry) {
		entry->group = group;
		entry->inode = inode;

		hlist_add_head(&entry->i_list, &inode->i_fsnotify_mark_entries);
		list_add(&entry->g_list, &group->mark_entries);

		fsnotify_get_mark(entry); /* for i_list and g_list */

		atomic_inc(&group->num_marks);

		fsnotify_recalc_inode_mask_locked(inode);
	}

	spin_unlock(&inode->i_lock);
	spin_unlock(&group->mark_lock);
	spin_unlock(&entry->lock);

	if (lentry) {
		ret = -EEXIST;
		iput(inode);
		fsnotify_put_mark(lentry);
	} else {
		__fsnotify_update_child_dentry_flags(inode);
	}

	return ret;
}

/**
 * fsnotify_unmount_inodes - an sb is unmounting.  handle any watched inodes.
 * @list: list of inodes being unmounted (sb->s_inodes)
 *
 * Called with inode_lock held, protecting the unmounting super block's list
 * of inodes, and with iprune_mutex held, keeping shrink_icache_memory() at bay.
 * We temporarily drop inode_lock, however, and CAN block.
 */
void fsnotify_unmount_inodes(struct list_head *list)
{
	struct inode *inode, *next_i, *need_iput = NULL;

	list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
		struct inode *need_iput_tmp;

		/*
		 * We cannot __iget() an inode in state I_CLEAR, I_FREEING,
		 * I_WILL_FREE, or I_NEW which is fine because by that point
		 * the inode cannot have any associated watches.
		 */
		if (inode->i_state & (I_CLEAR|I_FREEING|I_WILL_FREE|I_NEW))
			continue;

		/*
		 * If i_count is zero, the inode cannot have any watches and
		 * doing an __iget/iput with MS_ACTIVE clear would actually
		 * evict all inodes with zero i_count from icache which is
		 * unnecessarily violent and may in fact be illegal to do.
		 */
		if (!atomic_read(&inode->i_count))
			continue;

		need_iput_tmp = need_iput;
		need_iput = NULL;

		/* In case fsnotify_inode_delete() drops a reference. */
		if (inode != need_iput_tmp)
			__iget(inode);
		else
			need_iput_tmp = NULL;

		/* In case the dropping of a reference would nuke next_i. */
		if ((&next_i->i_sb_list != list) &&
		    atomic_read(&next_i->i_count) &&
		    !(next_i->i_state & (I_CLEAR | I_FREEING | I_WILL_FREE))) {
			__iget(next_i);
			need_iput = next_i;
		}

		/*
		 * We can safely drop inode_lock here because we hold
		 * references on both inode and next_i.  Also no new inodes
		 * will be added since the umount has begun.  Finally,
		 * iprune_mutex keeps shrink_icache_memory() away.
		 */
		spin_unlock(&inode_lock);

		if (need_iput_tmp)
			iput(need_iput_tmp);

		/* for each watch, send FS_UNMOUNT and then remove it */
		fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0);

		fsnotify_inode_delete(inode);

		iput(inode);

		spin_lock(&inode_lock);
	}
}
Commit	Line	Data
3be25f49 EP	1	/*
	2	* Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
	3	*
	4	* This program is free software; you can redistribute it and/or modify
	5	* it under the terms of the GNU General Public License as published by
	6	* the Free Software Foundation; either version 2, or (at your option)
	7	* any later version.
	8	*
	9	* This program is distributed in the hope that it will be useful,
	10	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	11	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	12	* GNU General Public License for more details.
	13	*
	14	* You should have received a copy of the GNU General Public License
	15	* along with this program; see the file COPYING. If not, write to
	16	* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
	17	*/
	18
	19	/*
	20	* fsnotify inode mark locking/lifetime/and refcnting
	21	*
	22	* REFCNT:
	23	* The mark->refcnt tells how many "things" in the kernel currently are
	24	* referencing this object. The object typically will live inside the kernel
	25	* with a refcnt of 2, one for each list it is on (i_list, g_list). Any task
	26	* which can find this object holding the appropriete locks, can take a reference
	27	* and the object itself is guarenteed to survive until the reference is dropped.
	28	*
	29	* LOCKING:
	30	* There are 3 spinlocks involved with fsnotify inode marks and they MUST
	31	* be taken in order as follows:
	32	*
	33	* entry->lock
	34	* group->mark_lock
	35	* inode->i_lock
	36	*
	37	* entry->lock protects 2 things, entry->group and entry->inode. You must hold
	38	* that lock to dereference either of these things (they could be NULL even with
	39	* the lock)
	40	*
	41	* group->mark_lock protects the mark_entries list anchored inside a given group
	42	* and each entry is hooked via the g_list. It also sorta protects the
	43	* free_g_list, which when used is anchored by a private list on the stack of the
	44	* task which held the group->mark_lock.
	45	*
	46	* inode->i_lock protects the i_fsnotify_mark_entries list anchored inside a
	47	* given inode and each entry is hooked via the i_list. (and sorta the
	48	* free_i_list)
	49	*
	50	*
	51	* LIFETIME:
	52	* Inode marks survive between when they are added to an inode and when their
	53	* refcnt==0.
	54	*
	55	* The inode mark can be cleared for a number of different reasons including:
	56	* - The inode is unlinked for the last time. (fsnotify_inode_remove)
	57	* - The inode is being evicted from cache. (fsnotify_inode_delete)
	58	* - The fs the inode is on is unmounted. (fsnotify_inode_delete/fsnotify_unmount_inodes)
	59	* - Something explicitly requests that it be removed. (fsnotify_destroy_mark_by_entry)
	60	* - The fsnotify_group associated with the mark is going away and all such marks
	61	* need to be cleaned up. (fsnotify_clear_marks_by_group)
	62	*
	63	* Worst case we are given an inode and need to clean up all the marks on that
	64	* inode. We take i_lock and walk the i_fsnotify_mark_entries safely. For each
65	* mark on the list we take a reference (so the mark can't disappear under us).
66	* We remove that mark form the inode's list of marks and we add this mark to a
67	* private list anchored on the stack using i_free_list; At this point we no
68	* longer fear anything finding the mark using the inode's list of marks.
69	*
70	* We can safely and locklessly run the private list on the stack of everything
71	* we just unattached from the original inode. For each mark on the private list
72	* we grab the mark-> and can thus dereference mark->group and mark->inode. If
73	* we see the group and inode are not NULL we take those locks. Now holding all
74	* 3 locks we can completely remove the mark from other tasks finding it in the
75	* future. Remember, 10 things might already be referencing this mark, but they
76	* better be holding a ref. We drop our reference we took before we unhooked it
77	* from the inode. When the ref hits 0 we can free the mark.
78	*
79	* Very similarly for freeing by group, except we use free_g_list.
80	*
81	* This has the very interesting property of being able to run concurrently with
82	* any (or all) other directions.
83	*/
84
85	#include <linux/fs.h>
86	#include <linux/init.h>
87	#include <linux/kernel.h>
88	#include <linux/module.h>
89	#include <linux/mutex.h>
3be25f49	90	#include <linux/spinlock.h>
164bc619	91	#include <linux/writeback.h> /* for inode_lock */
3be25f49 EP	92
	93	#include <asm/atomic.h>
	94
	95	#include <linux/fsnotify_backend.h>
	96	#include "fsnotify.h"
	97
	98	void fsnotify_get_mark(struct fsnotify_mark_entry *entry)
	99	{
	100	atomic_inc(&entry->refcnt);
	101	}
	102
	103	void fsnotify_put_mark(struct fsnotify_mark_entry *entry)
	104	{
	105	if (atomic_dec_and_test(&entry->refcnt))
	106	entry->free_mark(entry);
	107	}
	108
	109	/*
	110	* Recalculate the mask of events relevant to a given inode locked.
	111	*/
	112	static void fsnotify_recalc_inode_mask_locked(struct inode *inode)
	113	{
	114	struct fsnotify_mark_entry *entry;
	115	struct hlist_node *pos;
	116	__u32 new_mask = 0;
	117
	118	assert_spin_locked(&inode->i_lock);
	119
	120	hlist_for_each_entry(entry, pos, &inode->i_fsnotify_mark_entries, i_list)
	121	new_mask \|= entry->mask;
	122	inode->i_fsnotify_mask = new_mask;
	123	}
	124
	125	/*
	126	* Recalculate the inode->i_fsnotify_mask, or the mask of all FS_* event types
	127	* any notifier is interested in hearing for this inode.
	128	*/
	129	void fsnotify_recalc_inode_mask(struct inode *inode)
	130	{
	131	spin_lock(&inode->i_lock);
	132	fsnotify_recalc_inode_mask_locked(inode);
	133	spin_unlock(&inode->i_lock);
c28f7e56 EP	134
c28f7e56 EP	135	__fsnotify_update_child_dentry_flags(inode);
3be25f49 EP	136	}
	137
	138	/*
	139	* Any time a mark is getting freed we end up here.
	140	* The caller had better be holding a reference to this mark so we don't actually
	141	* do the final put under the entry->lock
	142	*/
	143	void fsnotify_destroy_mark_by_entry(struct fsnotify_mark_entry *entry)
	144	{
	145	struct fsnotify_group *group;
	146	struct inode *inode;
	147
	148	spin_lock(&entry->lock);
	149
	150	group = entry->group;
	151	inode = entry->inode;
	152
	153	BUG_ON(group && !inode);
	154	BUG_ON(!group && inode);
	155
	156	/* if !group something else already marked this to die */
	157	if (!group) {
	158	spin_unlock(&entry->lock);
	159	return;
	160	}
	161
	162	/* 1 from caller and 1 for being on i_list/g_list */
	163	BUG_ON(atomic_read(&entry->refcnt) < 2);
	164
	165	spin_lock(&group->mark_lock);
	166	spin_lock(&inode->i_lock);
	167
	168	hlist_del_init(&entry->i_list);
	169	entry->inode = NULL;
	170
	171	list_del_init(&entry->g_list);
	172	entry->group = NULL;
	173
	174	fsnotify_put_mark(entry); /* for i_list and g_list */
	175
	176	/*
	177	* this mark is now off the inode->i_fsnotify_mark_entries list and we
	178	* hold the inode->i_lock, so this is the perfect time to update the
	179	* inode->i_fsnotify_mask
	180	*/
	181	fsnotify_recalc_inode_mask_locked(inode);
	182
	183	spin_unlock(&inode->i_lock);
	184	spin_unlock(&group->mark_lock);
	185	spin_unlock(&entry->lock);
	186
	187	/*
	188	* Some groups like to know that marks are being freed. This is a
	189	* callback to the group function to let it know that this entry
	190	* is being freed.
	191	*/
a092ee20 EP	192	if (group->ops->freeing_mark)
a092ee20 EP	193	group->ops->freeing_mark(entry, group);
3be25f49	194
c28f7e56 EP	195	/*
	196	* __fsnotify_update_child_dentry_flags(inode);
	197	*
	198	* I really want to call that, but we can't, we have no idea if the inode
	199	* still exists the second we drop the entry->lock.
	200	*
	201	* The next time an event arrive to this inode from one of it's children
	202	* __fsnotify_parent will see that the inode doesn't care about it's
	203	* children and will update all of these flags then. So really this
	204	* is just a lazy update (and could be a perf win...)
	205	*/
	206
	207
1ef5f13c EP	208	iput(inode);
1ef5f13c EP	209
3be25f49 EP	210	/*
	211	* it's possible that this group tried to destroy itself, but this
	212	* this mark was simultaneously being freed by inode. If that's the
	213	* case, we finish freeing the group here.
	214	*/
	215	if (unlikely(atomic_dec_and_test(&group->num_marks)))
	216	fsnotify_final_destroy_group(group);
	217	}
	218
	219	/*
	220	* Given a group, destroy all of the marks associated with that group.
	221	*/
	222	void fsnotify_clear_marks_by_group(struct fsnotify_group *group)
	223	{
	224	struct fsnotify_mark_entry lentry, entry;
	225	LIST_HEAD(free_list);
	226
	227	spin_lock(&group->mark_lock);
	228	list_for_each_entry_safe(entry, lentry, &group->mark_entries, g_list) {
	229	list_add(&entry->free_g_list, &free_list);
	230	list_del_init(&entry->g_list);
	231	fsnotify_get_mark(entry);
	232	}
	233	spin_unlock(&group->mark_lock);
	234
	235	list_for_each_entry_safe(entry, lentry, &free_list, free_g_list) {
	236	fsnotify_destroy_mark_by_entry(entry);
	237	fsnotify_put_mark(entry);
	238	}
	239	}
	240
	241	/*
	242	* Given an inode, destroy all of the marks associated with that inode.
	243	*/
	244	void fsnotify_clear_marks_by_inode(struct inode *inode)
	245	{
	246	struct fsnotify_mark_entry entry, lentry;
	247	struct hlist_node pos, n;
	248	LIST_HEAD(free_list);
	249
	250	spin_lock(&inode->i_lock);
	251	hlist_for_each_entry_safe(entry, pos, n, &inode->i_fsnotify_mark_entries, i_list) {
	252	list_add(&entry->free_i_list, &free_list);
	253	hlist_del_init(&entry->i_list);
	254	fsnotify_get_mark(entry);
	255	}
	256	spin_unlock(&inode->i_lock);
	257
	258	list_for_each_entry_safe(entry, lentry, &free_list, free_i_list) {
	259	fsnotify_destroy_mark_by_entry(entry);
	260	fsnotify_put_mark(entry);
	261	}
	262	}
	263
	264	/*
	265	* given a group and inode, find the mark associated with that combination.
	266	* if found take a reference to that mark and return it, else return NULL
	267	*/
	268	struct fsnotify_mark_entry fsnotify_find_mark_entry(struct fsnotify_group group,
	269	struct inode *inode)
	270	{
	271	struct fsnotify_mark_entry *entry;
	272	struct hlist_node *pos;
	273
274	assert_spin_locked(&inode->i_lock);
275
276	hlist_for_each_entry(entry, pos, &inode->i_fsnotify_mark_entries, i_list) {
277	if (entry->group == group) {
278	fsnotify_get_mark(entry);
279	return entry;
280	}
281	}
282	return NULL;
283	}
284
285	/*
286	* Nothing fancy, just initialize lists and locks and counters.
287	*/
288	void fsnotify_init_mark(struct fsnotify_mark_entry *entry,
289	void (free_mark)(struct fsnotify_mark_entry entry))
290
291	{
292	spin_lock_init(&entry->lock);
293	atomic_set(&entry->refcnt, 1);
294	INIT_HLIST_NODE(&entry->i_list);
295	entry->group = NULL;
296	entry->mask = 0;
297	entry->inode = NULL;
298	entry->free_mark = free_mark;
299	}
300
301	/*
302	* Attach an initialized mark entry to a given group and inode.
303	* These marks may be used for the fsnotify backend to determine which
304	* event types should be delivered to which group and for which inodes.
305	*/
306	int fsnotify_add_mark(struct fsnotify_mark_entry *entry,
307	struct fsnotify_group group, struct inode inode)
308	{
309	struct fsnotify_mark_entry *lentry;
310	int ret = 0;
311
1ef5f13c EP	312	inode = igrab(inode);
	313	if (unlikely(!inode))
	314	return -EINVAL;
	315
3be25f49 EP	316	/*
	317	* LOCKING ORDER!!!!
	318	* entry->lock
	319	* group->mark_lock
	320	* inode->i_lock
	321	*/
	322	spin_lock(&entry->lock);
	323	spin_lock(&group->mark_lock);
	324	spin_lock(&inode->i_lock);
	325
3be25f49 EP	326	lentry = fsnotify_find_mark_entry(group, inode);
3be25f49 EP	327	if (!lentry) {
9f0d793b EP	328	entry->group = group;
	329	entry->inode = inode;
	330
3be25f49 EP	331	hlist_add_head(&entry->i_list, &inode->i_fsnotify_mark_entries);
	332	list_add(&entry->g_list, &group->mark_entries);
	333
	334	fsnotify_get_mark(entry); /* for i_list and g_list */
	335
	336	atomic_inc(&group->num_marks);
	337
	338	fsnotify_recalc_inode_mask_locked(inode);
	339	}
	340
	341	spin_unlock(&inode->i_lock);
	342	spin_unlock(&group->mark_lock);
	343	spin_unlock(&entry->lock);
	344
	345	if (lentry) {
	346	ret = -EEXIST;
1ef5f13c	347	iput(inode);
3be25f49	348	fsnotify_put_mark(lentry);
c28f7e56 EP	349	} else {
c28f7e56 EP	350	__fsnotify_update_child_dentry_flags(inode);
3be25f49 EP	351	}
	352
	353	return ret;
	354	}
164bc619 EP	355
	356	/**
	357	* fsnotify_unmount_inodes - an sb is unmounting. handle any watched inodes.
	358	* @list: list of inodes being unmounted (sb->s_inodes)
	359	*
	360	* Called with inode_lock held, protecting the unmounting super block's list
	361	* of inodes, and with iprune_mutex held, keeping shrink_icache_memory() at bay.
	362	* We temporarily drop inode_lock, however, and CAN block.
	363	*/
	364	void fsnotify_unmount_inodes(struct list_head *list)
	365	{
	366	struct inode inode, next_i, *need_iput = NULL;
	367
	368	list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
	369	struct inode *need_iput_tmp;
	370
	371	/*
	372	* We cannot __iget() an inode in state I_CLEAR, I_FREEING,
	373	* I_WILL_FREE, or I_NEW which is fine because by that point
	374	* the inode cannot have any associated watches.
	375	*/
	376	if (inode->i_state & (I_CLEAR\|I_FREEING\|I_WILL_FREE\|I_NEW))
	377	continue;
	378
	379	/*
	380	* If i_count is zero, the inode cannot have any watches and
	381	* doing an __iget/iput with MS_ACTIVE clear would actually
	382	* evict all inodes with zero i_count from icache which is
	383	* unnecessarily violent and may in fact be illegal to do.
	384	*/
	385	if (!atomic_read(&inode->i_count))
	386	continue;
	387
	388	need_iput_tmp = need_iput;
	389	need_iput = NULL;
	390
	391	/* In case fsnotify_inode_delete() drops a reference. */
	392	if (inode != need_iput_tmp)
	393	__iget(inode);
	394	else
	395	need_iput_tmp = NULL;
	396
	397	/* In case the dropping of a reference would nuke next_i. */
	398	if ((&next_i->i_sb_list != list) &&
	399	atomic_read(&next_i->i_count) &&
	400	!(next_i->i_state & (I_CLEAR \| I_FREEING \| I_WILL_FREE))) {
	401	__iget(next_i);
	402	need_iput = next_i;
	403	}
	404
	405	/*
	406	* We can safely drop inode_lock here because we hold
	407	* references on both inode and next_i. Also no new inodes
	408	* will be added since the umount has begun. Finally,
	409	* iprune_mutex keeps shrink_icache_memory() away.
	410	*/
	411	spin_unlock(&inode_lock);
	412
	413	if (need_iput_tmp)
	414	iput(need_iput_tmp);
	415
	416	/* for each watch, send FS_UNMOUNT and then remove it */
	417	fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
	418
419	fsnotify_inode_delete(inode);
420
421	iput(inode);
422
423	spin_lock(&inode_lock);
424	}
425	}